Flour based paper size

ABSTRACT

Internal fiber bonding laying of surface fuzz or fibers, with accompanying improvement in ancillary properties, e.g., improved surface and bursting strengths and printability, is accomplished by sealing the surface and/or body of paper or paperboard with a flour size in which the flour is present therein as a smooth, stable homogeneous colloidal co-solution, substantially free of undissolved fiber, of both the protein and starch fractions of the flour, the protein being present in substantially nondegraded form and the starch being present as a molecular weight reduced starch. The size can be produced by the steps, in either order, of subjecting a corn or other proteinaceous flour slurry to an instantaneous cooking at about 115*-175* C. and reducing the viscosity of the finished size to about 35-70 seconds (Dudley) by subjecting the flour in gelatinized or cooked form to the action of hydrogen peroxide or an enzyme. The resultant sizing material is viscosity stable and can be used to size paper and paperboard with a wet end press, at the breaker stacks, with a size press or water box on the calendar stacks or as an on-themachine coating operation, without the usual build up of scum resulting from separation of protein from the size.

United States Patent [i9] Ware et al. 1 Jan. 7, 1975 FLOUR BASED PAPER SIZE [57] ABSTRACT [75] Inventors; Franklyn O, Ware, Atchi on; Alan Internal fiber bonding laying of surface fuzz or fibers,

M, Hill, Top ka, both f K with accompanying improvement in ancillary properties, e.g., improved surface and bursting strengths and [73] Asslgnee: Lawrence Paper Company printability, is accomplished by sealing the surface Lawrence Kans' and/or body of paper or paperboard with a flour size [22] Filed: Jan. 29, 1973 in which the flour is present therein as a smooth, stable homogeneous colloidal co-solution, substantially [2]] App! 327444 free of undissolved fiber, of both the protein and Related US. Application Data starch fractions of the flour, the protein being present [63] continuatiommpart of Sen NOS 141,198, May 7 in substantially non-degraded form and the starch 97 p 775 and s m, 273,4771), belng present as a molecular weight reduced starch. 20, 1972, abandoned. The size can be produced by the steps, in either order, of subjecting a corn or other proteinaceous flour [52] US. Cl 106/150, 106/151, 106/162, lurry o an instantaneous cooking at about 115175 127/32, 117/156 C. and reducing the viscosity of the finished size to [51] Int. Cl C08h 7/00 about 35-70 seconds (Dudley) by subjecting the flour [58] Field of Search 106/162, 210, 213, 150, in gel iniz orcooked form to the action of hydro- 106/151; 127/32 gen peroxide or an enzyme. The resultant sizing material is viscosity stable and can be used to size paper [56] References Cited and paperboard with a wet end press, at the breaker UNITED STATES PATENTS stacks, with a size press or water box on the calendar 1 391 065 9/1921 Lenders 127/32 stacks or as an on-the-machine coating operation, 2:466l72 4/1949 Kesler without the usual build up of scum resulting from sep- 2,520:597 8/1950 Griffin. 127/32 arano" of Protein from the 5116- 2,635,068 4/1953 Rees 127/32 3,137,592 6/1964 Protzman 106/210 X Primary Examiner-Theodore Morris Attorney, Agent, or Firm-Miller, Raptes & White 9 Claims, 1 Drawing Figure 29 STEAM STEAM q 2/ o JET 2a JET 29 (OOKER 5;, COOKER a; n

a a l 97 36 i &1 g? WATER n) 77 P CONDENSATE 7? SIZING DISCHARGE 7 EGUIPlil-JVT PATENTED JAN 7 I875 a Sims m E2528 EmzmSem QENR FLOUR BASED PAPER SIZE This application is a continuation-in-part of our prior filed applications Ser. No. 141,198, filed May 7, 1971,

now U.S. Pat. No. 3,775,144 issued Nov. 27, 1973 and- Ser. No. 273,477, filed July 20, 1972, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a method of sizing paper and paperboard with a flourbased size, to the sizes employed herein and to the resulting sized paper products.

Paperand paperboard are conventionally sized with a wet milled pure starch produced from corn, wheat or tapioca. The type of sizing equipment employed is related to the type of machine and the grades of paper produced, e.g., wet end press, water boxes at the breaker stack, size press, water boxes at the calendar stack or adapting on-the-machine coating equipment, or a combination thereof. The solids-viscosity relationship of the size is determined by the requirements of the paper or paperboard in its end use. The solidsviscosity relationship of the size is adjusted by acid hydrolysis, enzyme conversion or peroxide, chlorine or other oxidation.

Thevalues achieved by sizing areinternal bonding, which is measured by the Mullen Test (bursting pressure in lbs/sq. in.); laying down of surface fuzz or fibers; and increased surface strengths, e.g., as measured by Dennison wax test, IGT test, cellophane tape fiberlay test or ink tack test. Since the surface of paper to be printed must print without rupture on a press at the speed and with the tack of the ink employed, other values, e.g., brittleness, rigidity, folding properties and ink penetration are also important for such papers. Any one or all or combinations of these values can be important, depending on the intended end use. The amount of dry pick up and distribution in the sheet are important relative to the development of these properties. The amount of dry pick up, as well as machine performance, is determined by the solids-viscosity rela tionship of the size."

Flours have not conventionally been employed as sizing agents because in the operation of any of the papermaking equipment in use today, there is a separation of the protein from the flour, which builds up as a scum making wash-ups and resulting down time far too frequent and expensive for even consideration of a flourbased size.

In our prior filed application Ser. No. 141,198, we disclose an instantaneous method of cooking a flour slurry to produce a stable flour paste useful, e.g., as an adhesive in the production of corrugated paperboard. The present invention employs a version of that method which produces a flour paste with a solids viscosity relationship which renders it suitable for use as a paper size.

Several methods for instantaneous cooking of, e.g., starch and flour slurries, have been developed. See U.S. Pat. Nos. 2,609,326, 2,717,213; 3,133,836; 3,228,781; 3,308,037; and 3,450,549.

The use of enzyme converted starch in paper sizes to obtain sizes of lower viscosities is conventional. See, e.g., U.S. Pat. Nos. 3,149,049 and 3,450,549. For enzymatic treatments of flour, see, e.g., U.S. Pat. Nos. 2,258,741; 2,824,037 and 3,163,549.

U.S. Pat. No. 3,137,592 describes a process for the production of a homogeneous gelatinized starch product by heating at 250 C. for about 0.5 to about 5 minutes. The patent states that the starch need not be highly refined, i.e., it may contain small proportions of non-starch material such as protein, fat and fiber. it does not, however, state that flour, which contains substantial proportions of protein and fiber, can be employed. Moreover, the patented process would severely degrade the protein fraction of flour and would not result in a modified flour which would form a smooth, stable homogeneous colloidal cosolution, substantially free of undissolved fiber, of both the protein and starch fractions of the flour.

Because of the obvious economic advantages which would result if a flour-containing adhesive could be produced which performed satisfactorily in commercial production, considerable effort has been directed to the production of a commercially acceptable flourbased corrugated paperboard adhesive. See U.S. Pat. Nos. 2,051,025; 2,102,937; 2,212,557; 2,291,586; 2,466,172; 2,520,597; 2,881,086; 2,999,028; 3,163,549; and 3,251,703.

Bauer, U.S. Pat. No. 2,051,025 claims a process for forming corrugated paperboard employing as adhesive the mixture of gelatinized flour or starch and an ungelatinized portion as a carrier claimed in U.S. Pat. No. 2,102,937. However, this process, known as the Stein- Hall process, as developed and as widely Used commercially today, employs starch exclusively. Bauer U.S. Pat. No. 2,212,557 discloses a potential adhesive composition which employs as a carrier a hydrosol of silica, alumina or magnesia, a natural gum, or one comprising gluten.

Galber and Dike, U.S. Pat. No. 2,291,586 discloses the use of a seedmeal flour-based adhesive for making plywood under heat and pressure.

As pointed out by Kesler and Hicks, U.S. Pat. No. 2,466,172, when uncooked flour is employed as an adhesive, no adhesive value is obtained from the starch portion of the flour and when the flour is cooked to gelatinize the starch fraction, the product is unsatisfactory for many uses and the starch becomes modified in a non-uniform manner due to the natural enzymes in the flour, resulting in a product of variable viscosity. The patentees state that prior efforts to use flour as an adhesive have, therefore, not been uniformly satisfactory commercially. That patent claims a process for avoiding non-uniformity by inactivating the natural enzymes in the flour at a pH of about 9l0 at about 56 C. prior to cooking.

Griffin, U.S. Pat. No. 2,520,597 approaches the problem of the adverse effect of the natural enzymes in flour in the usual cooking operation by instantly raising the flour slurry to a cooking temperature of 200-2l2 F. by dispersing the slurry in a large volume of boilingwater. This dilution technique produces a low-solids paste suitable for use as a textile size.

Wimmer, U.S. Pat. No. 2,881,086 states that when com flour is substituted for corn starch in the process of U.S. Pat. No. 2,051,025, the resulting material is very difficult to handle in large scale equipment for several reasons, one being the thixotropic character of the adhesive. Wimmer's claimed solution to the problem is a the use of paste formed from an esterified flour as the carrier. The chemical cost associated with this approach offsets much of the economic advantage of the use of flour instead of starch.

Horner, U.S. Pat. No. 2,999,028 also discusses the thixotropic disadvantage of the use of flour-based adhesives and states that consequently flours, as such, are not'ordinarily practical for corrugating machine operation. .That patent states that this disadvantage is avoided by the use of a gelatinized waxy starch or flour consisting essentially of 100 percent amylopectin as the cooked carrier portion of Stein-Hall type corrugating adhesive. Such flours are not standard commercial grades of flour and thus not widely and continuously available at prices which would make their use instead of conventional starch particularly attractive, assuming all other production factors were equal.

Vollnik and Hunt, U.S. Pat. No. 3,163,549 states that the protein in flour is detrimental to the properties of adhesives produced therefrom and claim a process in which a substantial portion of the protein of the flour is broken down prior to cooking the flour with a proteolytic enzyme having little amylolytic activity. This, of course, eliminates the possibility of achieving any adhesive effect from the protein present in flour.

Fortney and Hunt, U.S. Pat. No. 3,251,703 also states that prior attempts to use grain flours for the corn starch used in the Stein-Hall'process have not been successful. The patent notes that the thixotropic character and high viscosity of an adhesive formed from flour instead ofstarch precludes its use. When the proportion of gelatinized flour is reduced to overcome these effects, theresultant lowered viscosity and tackiness results in waste and unsatisfactory bonding. Their approach to the problem is the use as the uncooked portion of a finely ground flour of a specific particle size and quality in combination with a small percentage of certain gums as a carrier therefor. This process, like that of U.S. Pat. No. 2,999,028, is limited as to the type of flour which can be used. Neither process can use common commercial grades of flour, which offer the greatest economic advantage over starch if they could successfully be'substituted in the Stein-Hall process.

For other art on the treatment of flour, starch, and processes for producing adhesives,see U.S. Pat. Nos.

3,337,414; 3,423,239; 3,434,901; and 3,490,922.

OBJECTS OF THE INVENTION It is an object of this invention to provide a method of sizing paper and paperboard with a flour size. Another object is the provision of a flour-based size useful for the sizing of paper and paperboard. Another object is the provision of novel flour-sized papers and paperboards. Other objects will be apparent to those skilled in the art to which thisinvention pertains.

SUMMARY: OF THE INVENTION According to this invention paper and paperboard are sized with a flour size in which internal fiber bonding laying of surface fuzz or fibers, with accompanying improvement in ancillary properties, e.g., improved degraded form and the starch being present as a molecular weight reduced starch. The size can be produced by the steps, in either order of subjecting a corn or other proteinaceous flour slurry to an instantaneous cooking at about 1 l5175 C. and reducing the viscosity of the finished size to about 35-70 seconds (Dudley) by subjecting the flour in gelatinized or cooked form to the action of hydrogen peroxide or an enzyme.

DETAILED DISCUSSION The flour-based sizes of this invention have surprisingly advantageous properties which distinguish them from the flour'based sizes of the prior art. Moreover, they perform as well as or better than starch sizes on commercial paper making equipment. They do not exhibit the sludge and scum build-up in production equipment which heretofore has precluded the economic use of flour-based instead of starch-based sizes. The sizes of thisinvention have a smooth texture which is quite different from the granular texture of conventional flour pastes. Itis a homogeneous dispersion of both the 'protein and starch fractions of a proteinaceous flour with substantially higher tack than conventional pastes. It clings tenaciously to paper, filaments, yarn, metal and other articles to which it is applied. Its higher adhesiveness can readily be demonstrated by dipping a steel rod in the paste and observing the rate at which it is removed with running water, compared to a conventional flour paste of the same solids content. The properties, e.g., bond strength, of materials bonded with the paste are as good or better than those obtained with a starch paste of the same solids content.

The sizes of this invention consist essentially of a cooked proteinaceous flour paste. The term proteinaceous flour as usedherein means a flour containing substantial amounts of both protein and starch, the cooked paste produced therefrom being a stable colloidal co-solution of the protein and starch fractions thereof. Also present in the pastes in solubilized or substantially solubilized form are the other ingredients normally associated with proteinaceous flours, e.g., fiber, ash, traces of oil and soluble sugars.

The flour paste of the sizes of this invention is a smooth, homogeneous dispersion which varies in texture from smooth, creamy and semi-opaque solutionsuspension to a clear, transparent solution, depending on whether a portion only or all of the fibrous fraction of the flour is dissolved. All are characterized by the protein fraction of the flour being in stable co-solution, in substantially non-degraded form, with a molecular weight reduced modification of the starch fraction of the flour. This marriage of the protein and starch of the flour is unique and is responsible for the improved properties of the paste and sizes of this invention produced therefrom. Heretofore, the protein and/or fibrous fractions of flours caused problems which interfered with the use of flour as a substitute for starch in paper sizes. In the sizes of this invention, the protein fraction enhances their properties.

The protein fraction of the flour is present in the flour paste of the sizes of this invention in substantially non-degraded form, i.e., it retains the physical properties possessed by soluble proteins in solution, in contradistinction to the flour pastes of U.S. Pat. No. 3,163,549 in which the. protein has been degraded with proteolytic enzymes.

The presence of the protein fraction in the flour in non-degraded form as a stable co-solution with the starch fraction is a novel and characterizing feature of the sizes of this invention. It is known that flour proteins can be placed in colloidal solution at an alkaline pH at temperatures below the gelling temperature of starch. This procedure cannot be used to form a cosolution of both the protein and starch fractions because solubilization of the starch fractions requires a higher temperature, which results in severe degradation of the protein fraction. lf flour is cooked conventionally, none or only an insubstantial portion of the protein is solubilized in non-degraded form. If the pro tein and starch fractions are separately solubilized and thereafter blended, a stable co-solution does not result. The resulting blend has poorer adhesive properties than either of the solutions separately.

In contradistinction, the technique employed to produce the novel flour pastes of this invention, i.e., sub stantially instantaneous heating of the flour slurry to a temperature substantially above 100 C. at about neutrality or alkaline or a slightly acid pH, while subjecting the slurry to high mechanical stress, and thereafter promptly cooling the cooked paste to below the degradation temperature of the protein fraction, results in a stable co-solution of all or substantially all of both the starch and the protein fractions of the flour without substantial degradation .of the protein.

The flour pastes of this invention are free from or substantially free from the large, e.g., -30 percent, undissolved particulate matter normally present in starch pastes produced from conventional mill grades of flour, e.g., broken hulls and other fibrous matter and undissolved proteinaceous materials, which impart a granular texture to a conventional cooked flour pastes. This substantial freedom from particulate matter is apparently due to the combination of high cooking temperature and high mechanical stress to which the flour paste is subjected during the cooking step. Although finer grades of flour do not contain the large gross particles present in mill grades of flour, even the finer grades of flour produce a granular textured paste when cooked conventionally because of the large amount of finely divided fibrous and proteinaceous material which remains undissolved.

[n the flour pastes of the sizes of this invention, all of substantially all of the starch fraction of the flour is present in molecular weight reduced form as a colloidal co-solution with the protein fraction. Any undissolved material is relatively low in starch content. The clear solutions are completely or substantially free of undissolved material.

As used herein the term starch fraction means the carbohydrate fraction separable from flours by conventional physical means. The term protein fraction means the proteinaceous fraction remaining after the starch fraction has been separated. This ordinarily is associated with fiber, ash, traces of oil and sugars present in flours.

The starch fraction of the flour in the flour paste is present essentially as molecular weight reduced, referably enzymatically converted or H 0 oxidized starch so as to reduce the viscosity of the paste at any selected solids level. Because the viscosity of the finished size can be readily regulated by regulating the degree of enzyme conversion or H 0 oxidation, it is ordinarily preferred to maintain the desired solids-viscosity relationship of the finished size by varying the degree of molecular weight reduction rather than by varying the solids content of the flour paste in the final size or other means. Because of their high adhesion values, the novel sizes can be used at substantially lower solids content than the starch sizes of the prior art without losing requisite sizing properties.

Although H 0 is ordinarily employed, other equivalent chemical means can also be employed which reduce the molecular weight of the starch and do not significantly degrade the protein fraction. The enzymatic or H 0 conversion of the starch portion of the flour can be conducted on the gelatinized flour prior to or after cooking to form the stable co-solution of the protein and starch fractions.

The flour used in the preparation of the sizes of this invention is preferably corn flour. For economy sake, mill grade yellow corn flour is preferred where color in the finished size is not objectionable, e.g., cardboard and Kraft paper. When a size which is relatively free from color is desired, e.g., size suitable for bond and other grades of white paper, white corn flour is particularly advantageous. However, other proteinaceous flours can be used, e.g., milo, wheat, buckwheat, rye, barley, oat and other grain flours. ln contradistinction to the process of US. Pat. No. 3,251,703, which requires the use of an uncooked flour having a particle size such that at least 80 percent passes a U.S.S. No. 200 sieve and not more than 1 percent remains on a U.S.S. No. sieve, ordinary straight mill grades of flour, e.g., about 35 mesh or finer, can be used to form the cooked flour paste and are preferred because of their lower cost. More highly refined grades, e.g., reduction flour, finely ground brewers grits and other grades of up to 300 mesh or higher can, however, be employed, if desired.

Although the starch and protein contents of the flour employed is usually determined by the particular flour employed, it will be apparent that the starch/protein ratio of the flour pastes of this invention can be regulated by the use or addition of a material having a protein content higher than grain flours, e.g., soybean flour, gluten, corn feed, or lower than grain flours, e.g., corn, wheat, rice or tapioca starch. The addition of an additional source of protein is useful when a low viscosity high tack, low-solids size is desired. A flour rich in protein, e.g., soybean flour, can also be added when using a flour lacking or relatively deficient in protein, e.g., rice or tapioca flour. The ratio of starch in these blends should be greater than 1:1, preferably at least 2:1.

The starting flour slurry is prepared in a conventional manner, i.e., uniformly dispersing the flour in water to the desired solids content. Any solids content up to that which will set up on cooking can be used, e.g., 5 to 45 percent, more preferably about 20 to 32 percent. The desired final solids content can be lowered, if desired, by dilution of the cooked paste with water.

In the cooking step, any conventional pH can be employed. However, the pH should not exceed that at which the protein is substantially degraded to nonproteins. A pH near neutrality is usually employed. A slightly acid pH, e.g., pH 6.6 6.8, is preferred when the flour is enzymatically converted prior to or after cooking. An alkaline pH, e.g., 9-13, preferably about 12, can be employed to reduce the viscosity of the finished adhesive, especially sizes in which the cooked portion is high in protein, e.g., -25 percent.

Although it is preferred that only flour and water be present in the slurry, other materials which have been employed to modify the characteristics of the finished size can also be present, e.g., inorganic or organic hydrosols, as described in U.S. Pat. No. 2,212,557 and 3,251,703.

Because of its protein content, the flour paste is more susceptible than starch pastes to bacterial, fungal or yeast degradation. Therefore, a preservative should be added if the paste is not used within 8l2 hours after cooling below 140 C., e.g., formaldehyde, the Dowacides, or any other preservative conventionally employed to inhibit microbiological activity.

The flour paste employed in the cooked flourcontaining sizes of this invention is produced by cooking the flour slurry in a manner in which the resulting paste is a smooth, stable homogeneous colloidal cosolution of at least a predominant portion of both the protein and starch fractions of the flour, the protein fraction being present in substantially non-degraded form and the starch fraction being present essentially as chemically unmodified or molecular weight reduced starch. In such a physical condition, the flour paste impart's surprisingly advantageous properties to starchslurry sizes which employ the flour paste as a carrier. Such a flour paste can be produced by cooking the flour slurry substantially instantaneously at temperatures above cooking temperatures conventionally employed when cooking flour, while subjecting the slurry to a high degree of agitation and shearing action in excess of that required for uniform blending. For apparatus suitable for imparting this excess mechanical energy, See U.S. Pat. No. 2,609,326; 2,717,213; 3,228,781; 3,308,037; 3,133,836; 3,337,414; and

3,450,549. A particular useful method employs steam to provide the requisite shearing force, using the cooking apparatus .of U.S. Pat. No. 3,211,564 or 3,133,836. Because the flour slurry mixes with the steam as they both pass through a highly restricted orifice or orifices, the steam and slurry are mixed at extremelyhigh velocities thereby imparting the mechanical energy necessary to break up the flour particles and produce a smooth, homogeneous co-solution of both the protein and starch fractions of the flour. Usually all or substantially all, e.g., at least 90 percent of the protein and the starch fractions of the flour are dissolved, the protein being present in substantially non-degraded form and the starch being present essentially as molecular weight reduced starch. At high temperatures, all of the flour particles, including the fibrous particles, are dissolved, thus producing a clear, transparent solution. At lower temperatures, not all of the fibrous fraction is solubilized so that the paste is no longer transparent but still has a characteristic creamy, smooth texture which is quite dissimilar from conventional flour pastes.

For another example of equipment used to subject the flour slurry to a high shearing force, see U.S. Pat. No. 2,526,599. High mechanical energy can also be provided with an ultrasonic disintegrator, e.g., the

Branson sonifier (Heat Systems Co., 60 Broad Hollow Road, Melville, N.Y. Adding air, heated to a tem- V perature which offsets the cooling effect by evaporation of the water in the slurry, to the steam employed in U.S. Pat. No. 3,21 1,564, will increase the velocity of the flour slurry through the orifices of the cooking apparatus, thereby providing a higher shearing force; Compressed air instead of steam, if heated sufficiently to provide the requisite heat to bring the slurry to the desired cooking temperature, will also increase the shearing force achieved in the apparatus of U.S. Pat. No. 3,211,564.

The cooking temperaturerequired to produce the cosolution which characterizes the novel flour pastes varies inversely with the mechanical energy provided during the cooking step, e.g., about 1 15 to about 175 C. or even higher, preferably about to 165 C., more preferably about to C. A cooking temperature is employed which results in substantially instantaneous cooking of the flour so as to ensure that no significant degradation of the proteinaceous fraction of the flour occurs. The use of injected steam to heat the slurry to the desired temperature is preferred because of the rapadity at which cooking temperature can be reached.

As stated above,'if the slurry is subjected to sufficient I mechanical energy while being cooked, a clear, transparent paste is produced. A lesser amount of energy produces a smooth, creamy semi-opaque paste. Both can be readily distinguishable by touch from the granular textured flour pastes prepared in a conventional manner. The novel sizes range in color from yellow (corn), pale violet (milo) to brown (wheat), to essentially colorless when using H 0 oxidation or white corn flour.

After cooking, the flour paste is cooled, preferably as rapidly as possible, to below cooking temperature, e.g., 120-80 C. Cooling by indirect means is inefficient and direct cooling is preferred. A convenient technique is releasing the hot paste into an evacuated chamber maintained at a partial pressure which cools the hot paste to the desired temperature by evaporation. A simpler alternative or additional technique is to cook at a higher solids content than the final solids content and then cool and dilute the hot paste with cold water to the desired final solids content.

In the finished size, the starch portion of the flour is molecular weight reduced because like a starch size of the same solids content, its viscosity would otherwise be too high for application with conventional sizing equipment,.which are maintained at about 130-150 F. or slightly higher. Therefore, in addition to a cooking step, the flour must be subjected to a molecular weight reduction step.

The reduction of the molecular weight of the starch portion of the flour paste is conducted on the gelatinized flour particles or preferably before the cooking step or, in the case of an H 0 oxidation, it can be conducted substantially simultaneously with the cooking step.

The flour can be subjected to an enzymatic viscosity reduction step while the flour is in a cooked or in an uncooked but gelatinized condition in a conventional manner using, e.g., a liquifying or saccharifying amylase, such as, for example, a-amylase, B-amylase,

glucoamylase, etc. The amount which is used is dictated by the solids content, time of incubation, temperature of incubation and desired viscosity of the finished size. Usually, enzymatic conversion is conducted at an enzyme concentration of about 0.05 to 1 percent, preferably about 0.1 percent, by weight calculated on total solids, e.g., about 3 to 15 minutes at 77 C. to several hours at 45 C., until reduction in molecular weight is achieved which imparts the desired viscosity to the final size, e.g., about 35 to 70, preferably about 40-45 seconds (Dudley viscometer). As is well known, the viscosity of paper sizes is conventionally measured at the temperature at which the size is maintained in use, i.e., about 130 F. Measurement at a higher temperature, e.g., about 150 R, will give a few seconds slightly lower value.

Asis well known, the degree of reduction in molecular weight by the enzyme is a function of time, temperature, pH and enzyme concentration. By the adjustment selection of pH and conversion temperature, the particular conversion time and enzyme concentration can be that which best meets the demands of the mill. The enzyme treatment time can run from 1 minute up to days, with the longer time, the greater storage capacity that is needed, and the shorter the time, the more difficult it is to maintain the properties of the size uniform. About 10 minutes is the most practical time for most mills. Enzyme concentration will be determined by conversion time, with the shorter time the higher the concentration and vice versa. With time, temperature and pH constant, viscosity-solids relationship can be controlled by adjustment only of enzyme concentration,with the higher the enzyme concentration, the lower the viscosity at any given solids level, and vice versa.

The enzyme action is halted in a conventional manner to prevent further breakdown of the starch molecule, preferably with heat, e.g., at about 121 C. or higher. At lower temperatures, e.g., 92-l00 C., enzyme inactivation is not instantaneous. Therefore, further viscosity reduction occurs during inactivation, which requires starting at a higher viscosity than the desired final viscosity. Chemical means, e.g., copper sulfate and sodium phosphate, can also be used as well as pH adjustment, e.g., .to about pH 4 or below, to interrupt viscosity reduction, or pH 11 or above to completely destroy the enzyme.

The enzyme conversion is preferably conducted prior to the cooking step, because the cooking step can then be employed to inactivate the enzyme.

In the most preferred procedure, a stream of a mixture of the starting flour, preferably yellow corn flour, slurry and enzyme is continuously heated, preferably instantaneously, to the gelatinization temperature of the flour and thereafter continuously maintained at an appropriate conversion temperature for the selected enzyme, employing conventional times, temperatures and enzyme concentrations. The time of enzyme conversion is employed which achieves the desired final viscosity within the range of 35-70 seconds (Dudley) at the requisite solids content employed.

The stream of enzyme-converted flour paste is then subjected to an instantaneous continuous cooking step described hereinafter to kill the enzyme and produce the requisite protein and starch colloidal co-solution resulting from the marriage of these two flour components. The stream of cooked size is then cooled and, after any reduction in solids content necessary to achieve the desired final value, stored until used. The requisite uniformity of solids pick-up during use is preferably achieved by adjusting solids content and then achieving the desired operating viscosity, by regulation of degree of enzyme converstion, preferably by regulating the enzyme concentration.

in the H 0 conversion version of the process of this invention, H 0 rather than enzyme is added to the flour slurry, preferably before cooking, the mixture is instantaneously cooked and then maintained at above C., preferably about the cooking temperature, e.g., about l50-l55 C. Oxidation can then be terminated by cooling and/or by the addition of a reducing agent, e.g., sodium bisulfite. The latter is preferably employed to ensure that no slow residual autooxidation occurs prior to use by the presence of peroxide radicals on the starch molecules. Uniformity of solids pick-up during use can be achieved by adjusting incubation time or amount of H 0 added to the flour paste. From about 1 oz. to 2 lbs. of 35% H O /l00 lbs. of flour solids, preferably 1 pound or less, is usually employed. When a light colored or essentially colorless size is desired, an amount of H 0 is employed which achieves the desired final color and the desired viscosity is achieved by varying the incubation time.

The solids content of the sizes of this invention can vary widely and is determined by the intended end-use, e.g., about 1 to 20 percent, with the viscosity always being in the range of about 35-70 secs. (Dudley viscometer), irrespective of the solids content. About l-2 percent is preferred to lay the surface fibers of paper, about 8-12 percent for internal sizing of Kraft paper, l0-l4 percent for internal sizing of bond paper and 18-20 percent for internal sizing of rag stock. The final viscosity is dictated by the solids pick-up desired for that end use, employing the equipment available for applying the size to the paper wet.

The cooked flour paste can be used to advantage as sizes wherever starch sizes are employing in paper production, e.g., surface or internal sizing. Because of their higher adhesive values, a lesser volume of flour size and/or a lower solids content is required to achieve the desired sizing effect than is required with conventional starch sizes.

A useful method for preparing the sizing material of this invention is to slurry the flour at 3 lbs/gal. with pH adjusted to 6.6 to 6.8 and a concentration of alpha amylase enzyme which gives the desired final viscositysolids relationship. A stream of the slurry is then brought to 88 C. and maintained at this temperature for about 10 minutes, either by passing the hot mixture through an elongate pipe engineered to give the 10 minute holding time at the rate the mixture is pumped through it or the mixture can be pumped into a conical shaped tank without agitation. As the enzyme reacts with the flour, the viscosity of the mixture is lowered and allows gravity to pull the material down uniformily enough so that the enzyme treatment, and thus the viscosity of the end product,is uniform. The enzyme converted material is then pumped to a second apparatus, e.g., a hydroheater, equipped with a back pressure valve so that the mixture can be brought to C or above substantially instantly. This kills the enzyme and forms the smooth stable homogeneous colloidal cosolution, substantially free of undissolved fiber, of both the protein and starch fractions of proteinaceous flour. The finished material can then be brought to any desired solids concentration by water addition.

A composite apparatus useful for the preparation of all of the novel flour-based sizes of this invention is shown schematically in the drawing. A flour and water slurry is maintained in uniform suspension in a slurry tank 1 by a lightning stirrer 3. A discharge line 5, fitted with a shut-off valve 7, provides communication from the bottom of tank 1 to a water supply and drain line 9, ata point between a shut-off valve 11 and a centrifugal pump 13 mounted in line 9. Mounted to the discharge end of centrifugal pump 13 is a two-way valve 15 to which is connected a recirculating line 17, which permits top filling of the tank with water and recirculation of the contents of the tank, and line 19, which communicates with a jet cooker (.l-lydroheater, Hy-

drothermal Equipment Corporation, Milwaukee, Wisconsin).

Fitted to the jet cooker 20 is a steam supply line 21, equipped with a shut-off valve 22. Communicatingwith the discharge end of jet cooker 20 is aline 23, fitted with a thermometer 24 and shut-off valve 25, which provides communication with a holding tank 31, either directly or via an elongate incubation line 27, fitted with shut-off valve 28. Incubation line 27 is also fitted with a series of by-pass valves 29 by which the effective length of incubation line 27 and thus the holding time therein can be varied. The conical shape of the holding tank 31 permits it to be used alternatively or in addition to line 27 as an incubation chamber with the gelatinized paste sinking to the bottom of the tank as its viscosity is reduced by the enzyme.

The bottom of holding tank 31 is fitted with a variable speed centrifugal pump 32, connected to a line 35 which provides communication with a second jet cooker 41, which is connected to a steam supply line 43 fitted witha shut-off valve 44.

The discharge end of jet cooker 41 is connected by line 45, which is fitted with a thermometer 47 and a back-pressure valve 49 to flash chamber 51. Vapor phase discharge line 53, fitted with a thermometer 55 and a steam gauge 57, provides communication from flash chamber 51 to the inlet end ofa water cooled heat exchanger 59. Uncondensed gases are removed from the heat exchanger through line 61, fitted with vacuum gauge 63 and vented to the atmosphere by a vacuum pump 65. Condensate is discharged from the heat exchanger through line 67 into a condensate reservoir 69, from which it is pumped by a centrifugal pump 71 through line 73 to the sewer.

A by-pass line 34, fitted with shut-off valve 35, provides a direct connection from jet cooker 20 to flash chamber 51. A second by-pass line 37, fitted with shutoff valve 38 provides direct communication from the incubation line 27 to flash chamber 51 via line 46, fitted with shut-off valve 36.

A rotary pump 75 in line 77, which is fitted with a water supply line 79 equipped with shut-off valve 81, pumps the liquid phase from flash chamber 51 to a size storage tank 87, equipped with a stirrer 89. Finished size is pumped by gear pump 91 through delivery line 93 to the sizing equipment for application to the paper web.

A by-pass line 83, fitted with a shut-off valve 85, provides direct communication to storage tank 87 from jet cooker 20 via line 34 or from incubation line 27 via line 37, or from jet cooker 41 via line 46.

The fiber used to produce paper employing the sizes of this invention are those conventionally employed.

All other ingredients conventionally employed in the formation of various grades of paper and paperboard, viz., rosin, alum, waxes, sodium silicate, glues, wet strength resins, cationic resins, etc., may be present in the furnish.

Without further elaboration, it is believed that one skilled in the art can, using the preceding description,

,utilize the present invention to its'fullest extent. The

following preferred specific embodiments are, therefore, to be construed as merely illustrative, and not limitative of the remainder of the disclosure in any way whatsoever.

EXAMPLE 1 With valve 7 closed, valve 11 open and valve 15 turned to recycle, slurry tank 1 is charged with 200 gallons of city water from line 9 and 800 pounds of yellow corn flour (80 mesh), and agitated with lightning mixer 3. To this flour slurry is added 12 ounces of 50 percent caustic soda to bring. the pH to 6.6 6.8. Seven ounces of Dexlo alpha amylase enzyme are then added to the slurry. With valve 7 closed, valve 11 is opened, which allows water to flow from the city water supply to positive displacement pump 13. Two-way valve 15 is turned to discharge, valve 28 is opened and by-pass valves 29 adjusted so as to provide an incubation time of about 10 minutes and valves 25, 35, 36 and 38 are closed. Steam inlet valve 22 is adjusted to heat the water in jet cooker 20 to 88 C., which discharges the water through line 23 and incubation line 27 and then to holding tank 31. The water is discharged into line 33, where positive displacement pump 32 pumps the liquid through line 33 to the second jet cooker 41. The steam inlet valve 44 is adjusted to give sufficient Btus so that at pounds of back pressure, obtained by adjustment of valve 49, the temperature is maintained at l55 C. on the thermometer 47. The water then discharges into the flash chamber 51'.

65 gallons per minute of 5 C. water are passed through the cooling coils of the heat exchanger 59. Steam discharges through 6-line 53'into heat exchanger 59 where it is condensed and the air is cooled to 44 C. The steam condensate drains into reservoir 69 and is pumped to the sewer by centrifugal pump 71.

Barometric pump (Nash) 65 creates a vacuum of 17 inches of mercury in the flash chamber, giving a resultant boiling point to the finished material of 77 C. The discharge from the flash chamber 51 is pumped by Viking rotary pump through line 77, with valve closed to the storage tank 87. The equipment is now in adjustment and the incubation line 27 is heated to its equilibrium temperature.

With the equipment in adjustment and the incubation line 27 heated, valve 1 1 is closed and valve 7 is opened. The flour slurry is transported by pump 13 to jet cooker 20 where it is mixed with an amount of steam sufficient to bring'the slurry to an incubation temperature of 85 C. and transported through the incubation line 27 which, with 156 feet of 13-inch pipe, gives exposure to slurry to C., which instantaneously kills the en-.

zyme and marries the protein and carbohydrate by forming a co-solution of a predominant portion or all of the protein and enzyme-converted starch fractions of the flour. If desired, steam in excess of that required to bring the slurry to the desired cooking temperature can be supplied so as to provide additional shearing action.

The flash chamber 51 now separates the excess steam and the vacuum created by pump 65 brings the boiling point of the flour paste to 77 C. at the 17 inches of mercury created, and the resultant excess steam is con densed in the heat exchanger 59. When sufficient mechanical energy is supplied, the enzyme-finished cooked flour paste is a transparent, bright yellow colloidal co-solution of both the proteinaceous portion of the flour, in substantially undegraded form, and the enzyme converted starch portion. It is substantially free from undissolved particulate material, with a viscosity (Dudley) of 40 sec. (12 percent solids) At lower temperatures, a-milky colored creamy textured colloidal solution is produced. The cooked flour paste is dis charged at the bottom of flash chamber 51 and a rotary pump (Viking) 75 transports it to storage tank 87 after being diluted with water from line 79 to a lower solids content, e.g., to a concentration of 0.2 to 1.5 lbs. solids per gallon of finished size. By varying the amount of enzyme or, more preferably the dwell time in incubation tube 27, the viscosity of the size can be maintained uniformly at the desired level, e.g., 35 to 70, preferably 40-45 sec. (Dudley viscometer) at. 130 F.

Pumping of the enzyme-converted paste is continued until slurry tank 1 is empty. Valve 7 is then closed and valve 11 is opened so that water clears the equipment and water appears in the discharge line 77, at which time the equipment is shut down.

EXAMPLE 2 Follow the procedure of Example 1 with one or more of the following variations:

a. employ to 50, preferably to 30 cc. of the enzyme per 100 lbs. of flour solids so as to vary the final viscosity of the size at the same solids content and incubation time; I

b. vary the incubation time from 5 to 30 min., preferably from 7 to 12 minutes;

c. vary the incubation temperature from 73 to 88 C., preferably 80 to 86 C.;

d. employ a flour slurry of 50 to 300, preferably 250 to 300 lbs/100 gals. water;

e. employ 100 to 1,000, preferably 150 to 250 cc/lOO lbs. of flour solids of 35% H 0 instead of the enzyme with an incubation time of 0 to 10, preferably 3 to 4 minutes;

f. employ white corn mill grade flour;

g. vary the cooking temperature in jet cooker 41 from 150 to 200, preferably 150 to 160;

h. dilute the cooked paste with water from line 79 to a final solids content of 0.15 to 1.5,preferably 0.75 to 1.0 lbs/gal.

EXAMPLE 3- Follow the procedure of Example 1 except use holding tank 31 as an incubation chamber by closing valves 28 and 29 and opening valve 25. The conical shape of tank 31 permits the gelatinized paste to sink to the bottom as its viscosity is lowered by the enzyme. Final vis' cosity can be regulated by varying the amount of enzyme employed or, more preferably, by varying the average dwell time in tank 31.

EXAMPLE 4 Using only the single jet cooker 20, the incubation line 27 and storage tank 87, by closing valves 25, 28, 35 and 36, opening valve and adjusting valve 38 to achieve the desired back pressure, pump a flour slurry, to which hs been added about 1 pound of 35% H 0 per lbs. of fiour, instead of the enzyme, from tank 1, to jet cooker 20 and adjust the steam valve 22 and valve 38 so that the contents are heated to about to C. Maintain the cooked paste at that temperature for about 4 minutes. Cool the paste and bring it to the desired solids content by dilution with water from line 79.

EXAMPLE 5 Follow the procedure of Example 4, but omit the incubation line 27 by closing valves 25, 29, 36 and 38 and opening valve 85 and adjusting valve 35 to the desired back pressure.

EXAMPLE 6 Follow the procedure of Example 1, except omit the enzyme from slurry tank I, maintain the first jet cooker at 155 C., cool (by means not shown) the cooked paste to 88 C. followed by injection of the enzyme before it enters incubation line 27 and maintain the second jet cooker at 125 C.

EXAMPLE 7 Follow the procedure of Example 4, employing a corn flour slurry of about 36% solids, except pump the cooked l-l o -converted paste from incubation line 27 to flash chamber 51 by closing valve 85 and opening valves 36 and 49 to produce a paste of about 32% solids by venting into flash chamber 59. Maintain solids constant by varying the water injected from line 79, if necessary. Maintain viscosity constant by varying the H 0 added to tank 11.

EXAMPLE 8 Follow the procedure of Example 4 except use mill grade white corn flour. A white colored size suitable for use with white paper or paperboard is obtained.

EXAMPLE 9 Follow the procedure of Examples 4 or 7 except inject the H 0 e.g., by a volume metering variable speed pump (not shown), into line 19 or line 23 instead of adding it to the slurry tank 1.

EXAMPLE 10 Yellow corn flour (A.D.M.) meeting the specifications of an 80 mesh corn flour (10% moisture, 8% protein, 0.75% fat) was slurried in tank 1 at 3 lbs. per gallon of water. The pH was adjusted to 6.8. To the slurry was added 25 cc. of Wallenstein liquid alpha amylase for each 100 lbs. (dry solids) of flour. The slurry was pumped at 6 gpm with a Moyno pump to first Hydroheater 20 (Hydrothermal Equipment Company, Milwaukee, Wisconsin). The steam was adjusted to bring the slurry to 90 C. The hot flour and enzyme mix was emptied into a round incubation tank 31 having a conical bottom and fitted with a second Moyno pump 32 equipped with a Reeves variable drive. After 10 minutes incubation time, the second Moyno pump 32, adjusted to pump just over 6 gpm., was started. The level in incubation tank 31 was maintained constant while the equipment was operating continuously by adjusting the Reeves drive of pump 32.

The second Moyno pump 32 pumped the enzymeconverted gelatinized starch slurry to the second Hydroheater 41 equipped with a back pressure valve 49 so that the temperature could be maintained at 155 C. The resultant cooked flour paste was adjusted to 8 percent solids with water from line 79.

Furnish was prepared of all kraft corrugated reclaimed fiber. To this was added 2 pounds rosin size and 3 pounds alum per ton, using a six-cylinder paper making equipment with a 66 inches trim. The speed was 205 f.p.m. The equipment was equipped with a water box on each side on the first set of calendar Dennison Fiber Size Wgt. Cal. Mullen Wax Lay Water both sides Water bottom sideflour size top side .108 99 14 Poor 63 .0175 in 18 Excellent The corn flour size ran exceptionally well with no evidence of foaming or build up of any sludge.

EXAMPLE ll Corn flour size prepared exactly as in Example 1 was diluted to 12 percent solids.

Grade 80 Jute liner furnish was prepared with corrugated reclaimed fiber as filler and kraft reclaimed fiber for outside plies, with 8 lbs. rosin size and 8 lbs. alum being added to furnish.

The grade 80 was run on six cylinder cylinder machine with 66 inches trim at 190 f.p.m. treated on both sides at the water boxes on the calendar stack with wet milled starch, Staley Caladex No. 41-1, then with water and then with the corn flour size. The flour size ran as well as the starch size, without any evidence of sludge or scum buildup. The results of its use as a size and a comparable starch size of the same solids content is set forth below.

from yellow corn flour, whose average cost was $3.80 per hundred weight less than the viscosity modified starch, a weight of 71 lbs. per thousand square feet was required to achieve a Mullen of 142, which is a drop of 5.5 lbs. per thousand square feet. in addition to the economic advantages of this weight reduction, of great significance is the fact that this weight reduction makes jute more attractive for the manufacture of corrugated paperboard used for shipping containers. Heretofore, jute was not a desired stock for corrugated paperboard intended for such use because of the added shipping weight which resulted from its use in order to achieve minimum Mullen requirements for any specified grade; Since jute is produced from recycled stock, the ecological advantages of a size which promotes the re-use of paper stock is self-evident.

In the manufacture of coated white paper, less of the white size ofthis invention, e.g., size produced from white corn flour or H 0 treated yellow corn size, is required than a corresponding pearl starch size. As a result, less opacifying and/or brightening agent is required to achieve target specifications or greater opacity and/or brightness values are achieved when using the same amount of size.

The white sizes of this invention are also useful for the internal bonding of the stock and performs as well as or better than pearl starch based size.

It will be apparent from the above that the term size comprises both internal and surface bonding of paper, i.e., their use as binder for surface coating formulations as well as internal size.

The preceding examples can be repeated with similar success by substituting the generically or specifically described reactants and/or operating conditions of this invention for those used in the preceding examples.

From the foregoing description, one skilled in the art can easily ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various usages and conditions.

What is claimed is:

l. A non-sludge forming flour size adapted for sizing paper consisting essentially of a cooked flour paste which is smooth stable homogeneous colloidal cosolution, substantially free of undissolved fiber, of both the protein and starch fractions of the flour, the protein fractions being present in substantially non-degraded form and the starch fraction being present in viscosity reduced form, said paste having a viscosity of about Fiber Dennison Size Cal. Mullen Wax Water Starch Size Flour Size Flour Size Fair Excellent Excellent Excellent 35-70 seconds (Dudley) at about F. and a solids content of about 1-20 percent and said stable cosolution being produced by cooking a slurry of an unmodified grain flour or a grain flour modified solely by a viscosity reducing treatment with an amylase or with hydrogen peroxide, substantially instantaneously at ll5l75 C. while subjecting the slurry to high mechanical stress.

2. A size according to claim 1 having a solids content of about 8-12 percent and a Dudley viscosity of about 40-45 sec. at 130 F.

3. A size according to claim 1 wherein the flour is com flour.

4. A size according to claim 3 wherein the flour is yellow corn flour.

5. A size material according to claim 3 wherein the flour is white corn flour.

6. A size according to claim 1 wherein the flour is a grain flour modified solely by a viscosity reducing treatlow corn flour. 

1. A NON-SLUDGE FORMING FLOUR SIZE ADAPTED FOR SIZING PAPER CONSISTING ESSENTIALLY OF A COOKED FLOUR PASTE WHICH IS SMOOTH STABLE HOMOGENEOUS COLLOIDAL CO-SOLUTION, SUBSTANTIALLY FREE OF UNDISSOLVED FIBER, OF BOTH THE PROTEIN AND STARCH FRACTIONS OF THE FLOUR, THE PROTEIN FRACTIONS BEING PRESENT IN SUBSTANTIALLY NON-DEGRADED FORM AND THE STARCH FRACTION BEING PRESENT IN VISCOSITY REDUCED FORM, SAID PASTE HAVING A VISCOSITY OF ABOUT 35-70 SECONDS (DUDLEY) AT ABOUT 130*F. AND A SOLIDS CONTENT OF ABOUT 1-20 PERCENT AND SAID STABLE CO-SOLTION BEING PRODUCED BY COOKING A SLURRY OF AN UNMODIFIED GRAIN FLOUR OR A GRAIN OF FLOUR MODIFIED SOLELY BY A VISCOSITY REDUCING TREATMENT WITH AN AMYLASE OR WITH HYDROGEN PEROXIDE, SUNSTANTIALLY
 2. A size according to claim 1 having a solids content of about 8-12 percent and a Dudley viscosity of about 40-45 sec. at 130* F.
 3. A size according to claim 1 wherein the flour is corn flour.
 4. A size according to claim 3 wherein the flour is yellow corn flour.
 5. A size material according to claim 3 wherein the flour is white corn flour.
 6. A size according to claim 1 wherein the flour is a grain flour modified solely by a viscosity reducing treatment with H2O2.
 7. A size according to claim 1 wherein the flour is corn flour, having a solids content of about 8-12 percent and a Dudley viscosity of about 40-45 sec. at 130* F.
 8. A size according to claim 7 wherein the starch fraction of the flour is molecular weight reduced by reaction with H2O2.
 9. A size according to claim 8 wherein the flour is yellow corn flour. 